Abstract: A disposable syringe comprises a syringe body (1), a plunger (40) mounted on a stem (50) slidable inside the syringe body (1), and an injection needle (10) integral with a needle-carrier (11) engageable with the fore end (2) of the syringe body (1) or the plunger, retaining means (20, 23, 24) able to retain spring means (30) under compression being provided integrally with the syringe body (1) and engagement means (59) able to cooperate with the retaining means (23) to release the spring means (30), when the plunger (40) has reached the end of its stroke, being provided integrally with said stem (50), so that the spring means (30) can act on the stem (50) to cause retraction thereof into the retracted position.